AsA2P is a stable derivative which is easily converted into ascorbic acid by dephosphorylation in the body and hence exhibits vitamin C activity. AsA2P is therefore widely used, for example, as a raw material for the preparation of cosmetics and medicines, particularly cosmetics, and as an additive to foodstuffs.
Processes for the preparation of AsA2P by chemical synthesis are known [for example, JP-A-30328/70, 15605/73 and 18191/77 and J. Org. Chem. 47, 3453, (1982)]. The use of enzymes of microbial origin for the preparation of AsA2P has been reported in the Abstract of Lectures at the meeting of Japanese Society of Agricultural Chemistry, 4 L-1, p. 696 (1987).
Chemical synthesis has already been used for the preparation of AsA2P on an industrial scale. However, chemical synthesis has the inherent disadvantage that, in addition to the desired phosphorylation at the 2-position, various phosphorylated isomers for example, at the 3- and 6-positions may be inevitably produced and thus it is difficult to obtain a high yield of AsA2P. Consequently, various attempts have been made to improve the production yield of AsA2P, for example, by introducing a protecting group or by selecting the operation conditions. However, the known processes of preparation are still complicated and expensive, and moreover, it is difficult to produce AsA2P with high purity.
In the known preparative method using an enzyme originating from a microorganism of the species Citrobacter freundii (cf. Abstracts of the Lectures at the meeting of Japanese Society of Agricultural Chemistry, 4 L-1, p.696 (1987)), it was reported that, in this case, a major proportion of the product is phosphorylated at the 6-position and that, in order to obtain AsA2P, it is necessary to introduce a protecting group (for example, isopropylidene) before the beginning of the reaction, and then to remove it after the completion of the reaction.
As disclosed in our EP-A-0,272,064, we have previously discovered that various microorganisms are capable of specifically phosphorylating ascorbic acid at the 2-position to form AsA2P in the presence of ATP.